Mechanical behavior, bonding nature and defect processes of Mo₂ScAlC₂: A new ordered MAX phase

In the present study, we employed density functional theory calculations to investigate the mechanical behavior, bonding nature and defect processes of the new ordered MAX phase Mo₂ScAlC₂. The mechanical stability of the compound is verified with its single crystal elastic constants. The new phase Mo₂ScAlC₂ is anticipated to be prone to shear along the crystallographic b and c axes, when a rational force is applied to the crystallographic a axis. The compressibility along the 〈001〉 direction under uniaxial stress is expected to be easier in Mo₂ScAlC₂. Additionally, the volume deformation should be easier in Mo₂ScAlC₂ than the isostructural Mo₂TiAlC₂. Mo₂ScAlC₂ is predicted to behave in a brittle manner. Due to its higher Debye temperature, Mo₂ScAlC₂ is expected to be thermally more conductive than Mo₂TiAlC₂. The cross-slip pining procedure should be significantly easier in Mo₂ScAlC₂ as compared to Mo₂TiAlC₂. The new ordered MAX phase Mo₂ScAlC₂ has a mixed character of strong covalent and metallic bonding with limited ionic nature. Both Mo–C and Mo–Al bonds are expected to be more covalent in Mo₂ScAlC₂ than those of Mo₂TiAlC₂. The level of covalency of Sc–C bond is somewhat low compared to a similar bond Ti–C in Mo₂ScAlC₂. Due to its reduced hardness Mo₂ScAlC₂, it should be softer and more easily machinable compared to Mo₂TiAlC₂. The intrinsic defect processes reveal that the level of radiation tolerance in Mo₂ScAlC₂ is not as high as in other MAX phases such as Ti₃AlC₂.